Systems and methods for facilitating access to edges of cartesian-coordinate space using the null space

ABSTRACT

Devices, systems, and methods for providing increased range of movement of the end effector of a manipulator arm having a plurality of joints with redundant degrees of freedom. Methods include defining a position-based constraint within a joint space defined by the at least one joint, determining a movement of the joints along the constraint within a null-space and driving the joints according to a calculated movement to effect the commanded movement while providing an increased end effector range of movement, particularly as one or more joints approach a respective joint limit within the joint space.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a Non-Provisional of and claims the benefit ofpriority from U.S. Provisional Patent Application No. 61/800,381 filedon Mar. 15, 2013 and entitled “Systems and Methods for FacilitatingAccess to Edges of Cartesian-Coordinate Space Using the Null Space”(Attorney Docket No. ISRG03800PROV/US), the full disclosure of which isincorporated herein by reference.

The present application is generally related to the followingcommonly-owned applications: U.S. application Ser. No. 12/494,695 filedJun. 30, 2009, entitled “Control of Medical Robotic System ManipulatorAbout Kinematic Singularities;” U.S. application Ser. No. 12/406,004filed Mar. 17, 2009, entitled “Master Controller Having RedundantDegrees of Freedom and Added Forces to Create Internal Motion;” U.S.application Ser. No. 11/133,423 filed May 19, 2005 (U.S. Pat. No.8,004,229), entitled “Software Center and Highly Configurable RoboticSystems for Surgery and Other Uses;” U.S. application Ser. No.10/957,077 filed Sep. 30, 2004 (U.S. Pat. No. 7,594,912), entitled“Offset Remote Center Manipulator For Robotic Surgery;” and U.S.application Ser. No. 09/398,507 filed Sep. 17, 1999 (U.S. Pat. No.6,714,839), entitled “Master Having Redundant Degrees of Freedom;” U.S.Provisional Application No. 61/654,755 filed Jun. 1, 2012, entitled“Manipulator Arm-to-Patient Collision Avoidance Using a Null-Space;” andU.S. Provisional Application No. 61/654,773 filed Jun. 1, 2012, entitled“System and Methods for Avoiding Collisions Between Manipulator ArmsUsing a Null-Space,” the disclosures of which are incorporated herein byreference in their entireties.

BACKGROUND OF THE INVENTION

The present invention generally provides improved surgical and/orrobotic devices, systems, and methods.

Minimally invasive medical techniques are aimed at reducing the amountof tissue which is damaged during diagnostic or surgical procedures,thereby reducing patient recovery time, discomfort, and deleterious sideeffects. Millions of “open” or traditional surgeries are performed eachyear in the United States; many of these surgeries can potentially beperformed in a minimally invasive manner. However, only a relativelysmall number of surgeries currently use minimally invasive techniquesdue to limitations in surgical instruments, and techniques, and theadditional surgical training required to master them.

Minimally invasive telesurgical systems for use in surgery are beingdeveloped to increase a surgeon's dexterity as well as to allow asurgeon to operate on a patient from a remote location. Telesurgery is ageneral term for surgical systems where the surgeon uses some form ofremote control, e.g., a servomechanism, or the like, to manipulatesurgical instrument movements rather than directly holding and movingthe instruments by hand. In such a telesurgery system, the surgeon isprovided with an image of the surgical site at the remote location.While viewing typically a three-dimensional image of the surgical siteon a suitable viewer or display, the surgeon performs the surgicalprocedures on the patient by manipulating master control input devices,which in turn control the motion of robotic instruments. The roboticsurgical instruments can be inserted through small, minimally invasivesurgical apertures to treat tissues at surgical sites within thepatient, often the trauma associated with accessing for open surgery.These robotic systems can move the working ends of the surgicalinstruments with sufficient dexterity to perform quite intricatesurgical tasks, often by pivoting shafts of the instruments at theminimally invasive aperture, sliding of the shaft axially through theaperture, rotating of the shaft within the aperture, and/or the like.

The servomechanism used for telesurgery will often accept input from twomaster controllers (one for each of the surgeon's hands) and may includetwo or more robotic arms or manipulators. Mapping of the hand movementsto the image of the robotic instruments displayed by the image capturedevice can help provide the surgeon with accurate control over theinstruments associated with each hand. In many surgical robotic systems,one or more additional robotic manipulator arms are included for movingan endoscope or other image capture device, additional surgicalinstruments, or the like.

A variety of structural arrangements can be used to support the surgicalinstrument at the surgical site during robotic surgery. The drivenlinkage or “slave” is often called a robotic surgical manipulator, andexemplary linkage arrangements for use as a robotic surgical manipulatorduring minimally invasive robotic surgery are described in U.S. Pat.Nos. 6,758,843; 6,246,200; and 5,800,423, the full disclosures of whichare incorporated herein by reference. These linkages often make use of aparallelogram arrangement to hold an instrument having a shaft. Such amanipulator structure can constrain movement of the instrument so thatthe instrument shaft pivots about a remote center of spherical rotationpositioned in space along the length of the rigid shaft. By aligningthis center of rotation with the incision point to the internal surgicalsite (for example, with a trocar or cannula at an abdominal wall duringlaparoscopic surgery), an end effector of the surgical instrument can bepositioned safely by moving the proximal end of the shaft using themanipulator linkage without imposing potentially dangerous forcesagainst the abdominal wall. Alternative manipulator structures aredescribed, for example, in U.S. Pat. Nos. 6,702,805; 6,676,669;5,855,583; 5,808,665; 5,445,166; and 5,184,601, the full disclosures ofwhich are incorporated herein by reference.

While the new robotic surgical systems and devices have proven highlyeffective and advantageous, still further improvements would bedesirable. For example, a manipulator arm may include additionalredundant joints to provide increased movements or configurations undercertain conditions. When moving surgical instruments within a minimallyinvasive surgical site, however, joints may become poorly conditioned orconfigured in such a way that limits the ability of the manipulator armto access its full range of motion, particularly when pivotinginstruments about minimally invasive apertures through large angularranges. In such cases, movement of the joints may inadvertently resultin limited joint motion of one or more joints upon approaching anassociated joint limit, thereby reducing the dexterity of themanipulator arm. Alternative manipulator structures have been proposedwhich employ software control over a highly configurable kinematicmanipulator joint set to restrain pivotal motion to the insertion sitewhile inhibiting inadvertent manipulator/manipulator contact outside thepatient (or the like). These highly configurable “software center”surgical manipulator systems may provide significant advantages, but mayalso present challenges. In particular, the mechanically constrainedremote-center linkages may have safety advantages in some conditions.Additionally, the wide range of configurations of the numerous jointsoften included in these manipulators may result in the manipulatorsbeing difficult to manually set-up in a configuration that is desirablefor a particular procedure. Nonetheless, as the range of surgeries beingperformed using telesurgical systems continues to expand, there is anincreasing demand for expanding the available configurations and therange of motion of the instruments within the patient. Unfortunately,both of these changes can increase the challenges associated with themotion of the manipulators outside the body, and can also increase theimportance of avoiding combinations of joint states that unnecessarilylimit the range of motion of the manipulator arm.

For these and other reasons, it would be advantageous to provideimproved devices, systems, and methods for surgery, robotic surgery, andother robotic applications, and it would be particularly beneficial ifthese improved technologies provided the ability to provide moreconsistent movement of the manipulator arm to improve range of motion ofthe instruments for at least some tasks and without significantlyincreasing the size, mechanical complexity, or costs of these systems,and while maintaining or improving their dexterity.

BRIEF SUMMARY OF THE INVENTION

The present invention generally provides improved robotic and/orsurgical devices, systems, and methods. In many embodiments, theinvention will employ highly configurable surgical robotic manipulators.These manipulators, for example, may have more degrees of freedom ofmovement than the associated surgical end effectors have within asurgical workspace. A robotic surgical system in accordance with thepresent invention typically includes a manipulator arm supporting arobotic surgical instrument and a processor to calculate coordinatedjoint movements for manipulating an end effector of the instrument. Thejoints of the robotic manipulators supporting the end effectors allowthe manipulator to move throughout a range of different configurationsfor a given end effector position and/or a given pivot point location.In one aspect, the invention provides improved range of motion andmaneuverability of the manipulator arm by defining a positioned-basedconstraint within a joint-space of two or more joints of the manipulatorand moving the joints of the manipulator within a null-space of theJacobian based on the position-based constraint to provide increasedrange of movement for one or more joints, particularly near the edges orjoint limits of the one or more joints.

In certain aspects, the robotic surgical system utilizes holonomic orposition-based paths that are defined within a Cartesian-coordinatespace of the manipulator arm and correspond to a desired movement of oneor more joints of a manipulator arm having a distal end effector. TheCartesian-coordinate space may be defined as the space of positions andorientations of any desired control frame. The control frame may be thetool-tip, a reference attached to the manipulator body but not at thetool tip (e.g. another part of the tool), a reference not attached tothe manipulator body but that is associated or moves with one of thelinks (e.g. formation flying with an imaginary point which is attachedthe manipulator) or a reference that is not attached or associated withthe manipulator (e.g. attached to a target anatomy), one possible use ofwhich would be a camera control. Virtual potential fields may becalculated within the joint-space or Cartesian-coordinate space and usedto determine joint velocities of the joints to effect movement of one ormore joints of the manipulator within a null-space toward theposition-based constraint or paths thereby providing improved range ofmovement of the one or more joints while maintaining a desired positionor state of an end effector. This approach allows for improved controlover the movement of one or more joints within a null-space,particularly in a manipulator arm utilizing a Jacobian based controllerin which the primary calculations of the one or more joints are based onvelocities rather than positions.

In one aspect, the joint-space may be defined by the hardstops of thejoints of the manipulator arm. The end-effector or tool-tip in theCartesian-coordinate space can move in a variety of ways depending onhow the null-space is used. Without use of the null-space, the sameCartesian-coordinate space position may be close or far from the jointspace limits (e.g. hardstops). Therefore, for the sameCartesian-coordinate space positions, the manipulator movement can becalculated so as to slide along the null motion manifold away from thejoint space limits or hardstops, thereby ensuring that the full range ofavailable Cartesian-coordiante space positions are utilized. Oneadvantage of these aspects is that when driving the manipulator arm inthe Cartesian-coordinate space, the null-space, which is an attribute ofthe mapping between the joint and Cartesian-coordinate space (e.g.indirectly mapping between the control frame and the hardstops) can beused to maximize utility.

In certain aspects, the position-based constraint is defined as one ormore feature or paths within the joint space, the feature/pathscorresponding to movement of the joints within a null-space such that astate of a distal portion of the manipulator arm is maintained. Theposition-based constraints may vary according to the kinematics of thejoints of a given manipulator arm so as to provide increased range ofjoint movement for the manipulator arm. The one or more paths maycomprise a series of curves or surfaces representing along whichmovement of at least two joints is within a null-space of the Jacobian,the shape of the paths, curves or surfaces being dependent on thekinematics of the manipulator, and in particular the relationshipbetween the joints defining the joint-space in which the constraint isdefined. In many of the embodiments described herein, the series ofcurves or surfaces are substantially parallel, the curves being along anouter pitch joint axis of the joint-space, the curves each openingtoward a pitch forward direction.

In one aspect, the path may include a single path (e.g. curve orsurface) that is translated or modified in response to a position of atleast one joint within the joint-space. For example, the path may be asingle curve/surface that is translated along the outer pitch axis as astate of the pitch joint moves along the outer pitch joint axis. Incertain embodiments, the potential field defined in the joint-space mayvary according to the position of the path within the joint-space. Forexample, as a curve or surface translates toward the pitch forward froman origin of the joints space, the surrounding potential field pulls thesubject joints towards one or both of a non-displaced lateral pivotjoint state lateral pivot or minimum forward pitch, while as the pathcurve translates in the backward pitch direction from the origin of thesub-space, the potential field pulls the joint states toward one or bothof a displaced lateral pivot joint and/or a non-displaced pitch jointstate.

In some embodiments, a manipulator arm may include additional redundantjoints to allow for various types of movement, such as a reconfigurationmovement in response to a user command or an external manualarticulation of a joint. Rather than relying on robotic devices that aremechanically constrained to pivot a tool about a fixed point in space,or robotic devices having passive joints which passively pivot about thetissues of a minimally invasive aperture, embodiments of the presentinvention may calculate a motion that includes pivoting a link of themanipulator linkage about an aperture site. The degrees of freedom ofthe robotic linkages supporting the end effectors can allow the linkageto move throughout a range of configurations for a given end effectorposition, and the systems may drive the linkages to configurations whichinhibit collisions involving one or more moving robotic structures.Set-up of highly flexible robotic linkages can be facilitated byprocessors which drive one or more joints of the linkage while thelinkage is being manually positioned.

In some embodiments, the invention allows for movement of themanipulator arm to be directed towards a pre-determined set ofconstraints when moving to effect one more tasks, such as a desired endeffector movement, a reconfiguration movement or various othersmovements. It should be noted that the manipulator arm need not bemechanically “locked” to the set of constraints, but rather theconstraints can be utilized to direct movement of one or more joints ofthe manipulator arm when moving according to one or more commandedmovements. The manipulator arm may include various movements or modes ofoperation in which joint movements of the manipulator arm are notlimited by the defined constraints.

In general, commanded movement of the manipulator arm to effect movementof the distal end effector utilizes movement of all the joints of themanipulator arm. Various other types of movement, such as a commandedreconfiguration movement may utilize the same joints as used inmanipulation of the end effector or may include various other selectedjoints or sets of joints. When effecting movement of a manipulator armhaving redundant degrees of freedom, the motion of the joints accordingto one or more of these types of movement may result in unnecessary orunpredictable movement of the manipulator arm. In addition, movement ofan upper portion of a manipulator arm may unnecessarily limit theavailable range of motion of an adjacent manipulator arm, particularlywhen adjacent manipulator arms are driven according to a collisionavoidance movement in addition to an end effector manipulation movement.To provide improved movement of the manipulator arms, the redundantdegrees of freedom may be used to determine one or more constraints todirect movement of the joints toward configurations having increasedrange of movement for one or more joints. The constraints may be definedin either the joint-space using joint velocities or withinCartesian-coordinate space using positions.

In one aspect, the movement of a manipulator arm having redundantdegrees of freedom utilized primary calculations based on jointvelocities, such as by using a Jacobian based controller. The system maydefine a set of holonomic or position based constraints, such as one ormore paths or curves, in either the joint-space or theCartesian-coordinate space. The constraints may be used to develop anartificial potential field to “pull” or direct the movement of themanipulator arm towards using movement of the joints within a null-spaceof the Jacobian. This allows the one or more joints of the manipulatorarm to move so as to increase the range of movement of one or morejoints within the joint-space, while maintaining a desired state of theend effector during commanded end effector movements.

In various embodiments, the invention provides a robotic systemcomprising a manipulator assembly for robotically moving a distal endeffector relative to a proximal base. The manipulator assembly has aplurality of joints, the joints providing sufficient degrees of freedomto allow a range of joint states for an end effector state. An inputreceives a command to effect a desired movement of the end effector. Aprocessor couples the input to the manipulator assembly and includes afirst module and a second module. The first module is configured to helpcalculate movements of the joints in response to the command so as tomove the end effector with the desired movement. The second module isconfigured to help drive at least one of the joints in response to anexternal articulation of another joint of the manipulator assembly, suchas a clutch mode.

In certain aspects of the present invention, a redundant degrees offreedom (RDOF) surgical robotic system with manipulate input isprovided. The RDOF surgical robotic system includes a manipulatorassembly, one or more user input devices, and a processor with acontroller. A manipulator arm of the assembly has a plurality of jointsproviding sufficient degrees of freedom that allow a range of jointstates for a given end effector state. In response to a receivedreconfiguration command entered by a user, the system calculatesvelocities of the plurality of joints within a null-space. The jointsare driven according to the reconfiguration command and the calculatedmovement so as to maintain the desired state of the end effector.Typically, in response to receiving a manipulation command to move theend effector with a desired movement, the system calculates end effectordisplacing movement of the joints by calculating joint velocities withina null-perpendicular-space of the Jacobian orthogonal to the null-space,and drives the joints according to the calculated movement to effect thedesired end effector movement. To provide increased maneuverability andrange of motion for the various other types of movements describedabove, the system may include a revolute proximal most joint thataffects the pitch of a distal instrument shaft of the manipulator and/ora distal revolute joint coupling an instrument to a proximal portion ofthe manipulator arm that effects a pivotal movement of the instrumentshaft laterally from a plane through which the portion of themanipulator arm proximal of the distal revolute joint extends. Thesejoints may be utilized in any of the embodiments described herein.

In another aspect of the invention, the manipulator is configured tomove such that an intermediate portion of the instrument shaft pivotsabout a remote center. Between the manipulator and the instrument, thereare a plurality of driven joints providing sufficient degrees of freedomto allow a range of joint states for an end effector position when theintermediate portion of the instrument shaft passes through an accesssite. A processor having a controller couples the input device to themanipulator. In response to a reconfiguration command, the processordetermines movements of one or more joints to effect the desiredreconfiguration so that the intermediate portion of the instrument iswithin the access site during the end effector's desired movement andmaintains the desired remote center location about which the shaftpivots. Typically, in response to receiving a manipulation command toeffect a desired end effector's movement, the system calculates endeffector displacing movement of the joints, comprising calculating jointvelocities within a null-perpendicular-space of the Jacobian orthogonalto the null-space, and drives the joints according to the calculatedmovement to effect the desired end effector movement in which theinstrument shaft pivots about the remote center.

In some embodiments, the manipulator includes a revolute joint couplingthe manipulator arm to the base. The desired state of the end effectormay include a desired position, velocity or acceleration of the endeffector. The manipulation command and the reconfiguration command maybe separate inputs, typically being received from separate users onseparate input devices, or may be separate inputs are received from thesame user. In some embodiments, the end effector manipulation command isreceived from an input device by a first user, such as a surgeonentering the command on a surgical console master input, while thereconfiguration command is received from an input device by a seconduser on a separate input device, such as a physician's assistantentering the reconfiguration command on a patient side cart inputdevice. In other embodiments, the end effector manipulation command andthe reconfiguration command are both received by the same user frominput devices at a surgical console.

In yet another aspect of the present invention, a surgical roboticmanipulator with a proximal revolute joint and a distal parallelogramlinkage is provided, the pivotal axis of the revolute jointsubstantially intersecting with the axis of the instrument shaft of theend effector, preferably at a remote center if applicable. The systemfurther includes a processor having a controller coupling the input tothe manipulator arm and configured to calculate a movement of theplurality of joints in response to a user input command. The system mayinclude an input device for receiving a reconfiguration command to movea first set of joints of the plurality of joints with a desiredreconfiguration movement within the null-space or may include a clutchmode that allows a user to manually reconfigure one or more joints ofthe manipulator arm within the null-space as to maintain the endeffector the desired state. The system may be configured to adjust ortranslate the positional constraints in response to a user drivenreconfiguration or a manual reconfiguration of the manipulator arm, suchas in a clutch mode, to allow for improved consistency andpredictability of one or more joints within the null-space, whilemaintaining the desired state of the end effector, while providing theadditional capability of a user input or manual reconfiguration.

A further understanding of the nature and advantages of the presentinvention will become apparent by reference to the remaining portions ofthe specification and drawings. It is to be understood, however, thateach of the figures is provided for the purpose of illustration only andis not intended as a definition of the limits of the scope of theinvention. Furthermore, it is appreciated than any of the features inany of the described embodiments could be modified and combined with anyof various other features described herein or known to one of skill inthe art and still remain within the spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an overhead view of a robotic surgical system in accordancewith embodiments of the present invention, the robotic surgical systemhaving a surgical station with a plurality of robotic manipulators forrobotically moving surgical instruments having surgical end effectors atan internal surgical site within a patient.

FIG. 1B diagrammatically illustrates the robotic surgical system of FIG.1A.

FIG. 2 is a perspective view illustrating a master surgeon console orworkstation for inputting surgical procedure commands in the surgicalsystem of FIG. 1A, the console including a processor for generatingmanipulator command signals in response to the input commands.

FIG. 3 is a perspective view of the electronics cart of FIG. 1A.

FIG. 4 is a perspective view of a patient side cart having fourmanipulator arms.

FIGS. 5A-5D show an exemplary manipulator arm.

FIGS. 6A-6B show an exemplary manipulator arm in the pitch forwardconfiguration and pitch back configurations, respectively.

FIG. 6C shows a graphical representation of the range of motion of thesurgical instrument tool tip of an exemplary manipulator arm, includinga cone of silence or conical tool access limit zone in each of the pitchforward and pitch back configurations.

FIG. 7A shows exemplary manipulator arms having a proximal revolutejoint that revolves the manipulator arm about an axis of a proximalrevolute joint.

FIG. 7B shows an exemplary manipulator arm and the associated range ofmotion and cone of silence, the exemplary manipulator arm having aproximal revolute joint that revolves the manipulator arm around an axisof a proximal revolute joint the movement of which can be used tomitigate the depicted cone of silence.

FIGS. 8 and 9 show an exemplary manipulator arms having a revolute jointnear the distal instrument holder.

FIGS. 10A-10C show sequential views of an exemplary manipulator armhaving a revolute joint near a distal instrument holder as the joint ismoved throughout its range of joint movement.

FIGS. 11A-11B show the revolved profile of an exemplary manipulator armhaving a distal revolute joint when the angular displacement of thejoint is 0° versus an angular displacement of 90°, respectively.

FIGS. 12A-12C show exemplary manipulator arms having a proximal jointthat translates a proximal joint supporting the manipulator arm about acurved path.

FIGS. 13A-13B graphically represent the relationship between thenull-space and the null-perpendicular-space of the Jacobian of anexemplary manipulator assembly.

FIG. 14 graphically illustrates an example of network path segments foruse in controlling movement of a manipulator assembly within thenull-space.

FIGS. 15-17 schematically illustrate methods in accordance anembodiment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally provides improved surgical and roboticdevices, systems, and methods. The invention is particularlyadvantageous for use with surgical robotic systems in which a pluralityof surgical tools or instruments may be mounted on and moved by anassociated plurality of robotic manipulators during a surgicalprocedure. The robotic systems will often comprise telerobotic,telesurgical, and/or telepresence systems that include processorsconfigured as master-slave controllers. By providing robotic systemsemploying processors appropriately configured to move manipulatorassemblies with articulated linkages having relatively large numbers ofdegrees of freedom, the motion of the linkages can be tailored for workthrough a minimally invasive access site. The large number of degrees offreedom allows a system operator, or an assistant, to reconfigure thelinkages of the manipulator assemblies while maintaining the desired endeffector state, optionally in preparation for surgery and/or whileanother use maneuvers the end effector during a surgical procedure.While aspects of the invention are generally described manipulatorshaving redundant degrees of freedom, it is appreciated that aspects mayapply to non-redundant manipulators, for example a manipulatorexperiencing or approaching a singularity.

The robotic manipulator assemblies described herein will often include arobotic manipulator and a tool mounted thereon (the tool oftencomprising a surgical instrument in surgical versions), although theterm “robotic assembly” will also encompass the manipulator without thetool mounted thereon. The term “tool” encompasses both general orindustrial robotic tools and specialized robotic surgical instruments,with these later structures often including an end effector which issuitable for manipulation of tissue, treatment of tissue, imaging oftissue, or the like. The tool/manipulator interface will often be aquick disconnect tool holder or coupling, allowing rapid removal andreplacement of the tool with an alternate tool. The manipulator assemblywill often have a base which is fixed in space during at least a portionof a robotic procedure, and the manipulator assembly may include anumber of degrees of freedom between the base and an end effector of thetool. Actuation of the end effector (such as opening or closing of thejaws of a gripping device, energizing an electrosurgical paddle, or thelike) will often be separate from, and in addition to, these manipulatorassembly degrees of freedom.

The end effector will typically move in the workspace with between twoand six degrees of freedom. As used herein, the term “position”encompasses both location and orientation. Hence, a change in a positionof an end effector (for example) may involve a translation of the endeffector from a first location to a second location, a rotation of theend effector from a first orientation to a second orientation, or acombination of both. When used for minimally invasive robotic surgery,movement of the manipulator assembly may be controlled by a processor ofthe system so that a shaft or intermediate portion of the tool orinstrument is constrained to a safe motion through a minimally invasivesurgical access site or other aperture. Such motion may include, forexample, axial insertion of the shaft through the aperture site into asurgical workspace, rotation of the shaft about its axis, and pivotalmotion of the shaft about a pivot point adjacent the access site.

Many of the exemplary manipulator assemblies described herein have moredegrees of freedom than are needed to position and move an end effectorwithin a surgical site. For example, a surgical end effector that can bepositioned with six degrees of freedom at an internal surgical sitethrough a minimally invasive aperture and may in some embodiments havenine degrees of freedom (six end effector degrees of freedom—three forlocation, and three for orientation—plus three degrees of freedom tocomply with the access site constraints), but will often have ten ormore degrees of freedom. Highly configurable manipulator assemblieshaving more degrees of freedom than are needed for a given end effectorposition can be described as having or providing sufficient degrees offreedom to allow a range of joint states for an end effector position ina workspace. For example, for a given end effector position, themanipulator assembly may occupy (and be driven between) any of a rangeof alternative manipulator linkage positions. Similarly, for a given endeffector velocity vector, the manipulator assembly may have a range ofdiffering joint movement speeds for the various joints of themanipulator assembly within the null-space of the Jacobian.

The invention provides robotic linkage structures which are particularlywell suited for surgical (and other) applications in which a wide rangeof motion is desired, and for which a limited dedicated volume isavailable due to the presence of other robotic linkages, surgicalpersonnel and equipment, and the like. The large range of motion andreduced volume needed for each robotic linkage may also provide greaterflexibility between the location of the robotic support structure andthe surgical or other workspace, thereby facilitating and speeding upset-up.

The term “state” of a joint or the like will often herein refer to thecontrol variables associated with the joint. For example, the state ofan angular joint can refer to the angle defined by that joint within itsrange of motion, and/or to the angular velocity of the joint. Similarly,the state of an axial or prismatic joint may refer to the joint's axialposition, and/or to its axial velocity. While many of the controllersdescribed herein comprise velocity controllers, such controllers mayalso include some position control aspects. Alternative embodiments mayrely primarily or entirely on position controllers, accelerationcontrollers, or the like. Many aspects of control system that can beused in such devices are more fully described in U.S. Pat. No.6,699,177, the full disclosure of which is incorporated herein byreference. Hence, so long as the movements described are based on theassociated calculations, the calculations of movements of the joints andmovements of an end effector described herein may be performed using aposition control algorithm, a velocity control algorithm, a combinationof both, and/or the like.

In one aspect, the tool of an exemplary manipulator arm pivots about apivot point adjacent a minimally invasive aperture. The system mayutilize a hardware remote center, such as the remote center kinematicsdescribed in U.S. Pat. No. 6,786,896, the entire contents of which areincorporated herein in its entirety. Such systems may utilize a doubleparallelogram linkage which constrains the movement of the linkages suchthat the shaft of the instrument supported by the manipulator pivotsabout a remote center point. Alternative mechanically constrained remotecenter linkage systems are known and/or may be developed in the future.Surprisingly, work in connection with various aspects of the inventionindicates that remote center linkage systems may benefit substantiallyfrom highly configurable kinematic architectures. In particular, when asurgical robotic system has a linkage that allows pivotal motion abouttwo axes intersecting at or near a minimally invasive surgical accesssite, the spherical pivotal motion may encompass the full extent of adesired range of motion within the patient, but may still suffer fromavoidable deficiencies, such as being poorly conditioned, beingsusceptible to arm-to-arm or arm-to-patient contact outside the patient,and/or the like. At first, adding one or more additional degrees offreedom that are also mechanically constrained to pivotal motion at ornear the access site may appear to offer few or any improvements in therange of motion. Nonetheless, such joints can provide significantadvantages by allowing the overall system to be configured in or driventoward a collision-inhibiting pose, by further extending the range ofmotion for other surgical procedures, and the like.

In another aspect, the system may utilize software to achieve a remotecenter, such as described in U.S. Pat. No. 8,004,229, the entirecontents of which are incorporated herein by reference. In a systemhaving a software remote center, the processor calculates movement ofthe joints so as to pivot an intermediate portion of the instrumentshaft about a pivot point determined, as opposed to a mechanicalconstraint. By having the capability to compute software pivot points,different modes characterized by the compliance or stiffness of thesystem can be selectively implemented. More particularly, differentsystem modes over a range of pivot points/centers (e.g., moveable pivotpoints, passive pivot points, fixed/rigid pivot point, soft pivotpoints) can be implemented as desired.

Despite the many advantages of a robotic surgical system having multiplehighly configurable manipulators, since the manipulators include arelatively large number of joints and links between the base andinstrument, manual positioning of the links can be challenging andcomplicated. Even when the manipulator structure is balanced so as toavoid gravitational effects, attempting to align each of the joints inan appropriate arrangement or to reconfigure the manipulator as desiredcan be difficult, time consuming, and may involve significant trainingand/or skill. The challenges can be even greater when the links of themanipulator are not balanced about the joints, such that positioningsuch a highly configurable structures in an appropriate configurationbefore or during surgery can be a struggle due to the manipulator armlength and the passive and limp design in many surgical systems.

These issues can be addressed by allowing a user, such as a physician'sassistant, to quickly and easily reconfigure the manipulator arm, whileand maintaining the desired end effector state, optionally even duringmovement of the end effector during a surgical procedure. One or moreadditional joints may be included in the manipulator arm to increase therange of motion and configurations of the manipulator arm to enhancethis capability. While providing additional joints may provide increasedrange of motion for certain tasks, various combinations of joint statesmay unnecessarily limit the available range of joint movement,particularly near the joint limits of one or more joints of themanipulator.

In some embodiments, calculated movement relating to various othertasks, such as an avoidance movement based on an autonomous algorithm,may overlay the access facilitating movement so that the one or morejoints may be moved to effect various other tasks, as needed. Examplesof such avoidance movement are described in U.S. Provisional ApplicationNo. 61/654,755 filed Jun. 1, 2012, entitled “Manipulator Arm-to-PatientCollision Avoidance Using a Null-Space;” and U.S. ProvisionalApplication No. 61/654,773 filed Jun. 1, 2012, entitled “System andMethods for Avoiding Collisions Between Manipulator Arms Using aNull-Space,” the disclosures of which are incorporated herein byreference in their entireties. The calculated movement that overlays thefacilitating movement of the one or more joints, however, is not limitedto the autonomous movement and may include various other movements, suchas a commanded reconfiguration movement or various other movements.

Embodiments of the invention may include a user input which isconfigured to take advantage of the degrees of freedom of a manipulatorstructure. Rather than manually reconfiguring the manipulator, the inputfacilitates use of driven joints of the kinematic linkage to reconfigurethe manipulator structure in response to entry of a reconfigurationcommand by a user. The user input for receiving the reconfigurationcommand may be incorporated into and/or disposed near the manipulatorarm. In some embodiments, the input comprises a centralized input deviceto facilitate reconfiguration of one or more joints, such as a clusterof buttons on the patient side cart or a joystick. Typically, the inputdevice for receiving the reconfiguration command is separate from theinput for receiving a manipulation command to effect movement of the endeffector. A controller of the surgical system may include a processorwith readable memory having joint controller programming instructions orcode recorded thereon which allows the processor to derive suitablejoint commands for driving the joints recorded thereon so as to allowthe controller to effect the desired reconfiguration in response toentry of the reconfiguration command. It is appreciated, however, thatthe invention may be used in a manipulator arm with or without areconfiguration feature.

In the following description, various embodiments of the presentinvention will be described. For purposes of explanation, specificconfigurations and details are set forth in order to provide a morethorough understanding of the embodiments. However, it will also beapparent to one skilled in the art that the present invention may bepracticed without various specific details. Furthermore, well-knownfeatures may be omitted or simplified in order not to obscure theembodiment being described.

Referring now to the drawings, in which like reference numeralsrepresent like parts throughout the several views, FIG. 1A is anoverhead view illustration of a Minimally Invasive Robotic Surgical(MIRS) system 10, in accordance with many embodiments, for use inperforming a minimally invasive diagnostic or surgical procedure on aPatient 12 who is lying down on an Operating table 14. The system caninclude a Surgeon's Console 16 for use by a Surgeon 18 during theprocedure. One or more Assistants 20 may also participate in theprocedure. The MIRS system 10 can further include a Patient Side Cart 22(surgical robot) and an Electronics Cart 24. The Patient Side Cart 22can manipulate at least one removably coupled tool assembly 26(hereinafter simply referred to as a “tool”) through a minimallyinvasive incision in the body of the Patient 12 while the Surgeon 18views the surgical site through the Console 16. An image of the surgicalsite can be obtained by an endoscope 28, such as a stereoscopicendoscope, which can be manipulated by the Patient Side Cart 22 so as toorient the endoscope 28. The Electronics Cart 24 can be used to processthe images of the surgical site for subsequent display to the Surgeon 18through the Surgeon's Console 16. The number of surgical tools 26 usedat one time will generally depend on the diagnostic or surgicalprocedure and the space constraints within the operating room amongother factors. If it is necessary to change one or more of the tools 26being used during a procedure, an Assistant 20 may remove the tool 26from the Patient Side Cart 22, and replace it with another tool 26 froma tray 30 in the operating room.

FIG. 1B diagrammatically illustrates a robotic surgery system 50 (suchas MIRS system 10 of FIG. 1A). As discussed above, a Surgeon's Console52 (such as Surgeon's Console 16 in FIG. 1A) can be used by a Surgeon tocontrol a Patient Side Cart (Surgical Robot) 54 (such as Patent SideCart 22 in FIG. 1A) during a minimally invasive procedure. The PatientSide Cart 54 can use an imaging device, such as a stereoscopicendoscope, to capture images of the procedure site and output thecaptured images to an Electronics Cart 56 (such as the Electronics Cart24 in FIG. 1A). As discussed above, the Electronics Cart 56 can processthe captured images in a variety of ways prior to any subsequentdisplay. For example, the Electronics Cart 56 can overlay the capturedimages with a virtual control interface prior to displaying the combinedimages to the Surgeon via the Surgeon's Console 52. The Patient SideCart 54 can output the captured images for processing outside theElectronics Cart 56. For example, the Patient Side Cart 54 can outputthe captured images to a processor 58, which can be used to process thecaptured images. The images can also be processed by a combination theElectronics Cart 56 and the processor 58, which can be coupled togetherso as to process the captured images jointly, sequentially, and/orcombinations thereof. One or more separate displays 60 can also becoupled with the processor 58 and/or the Electronics Cart 56 for localand/or remote display of images, such as images of the procedure site,or other related images.

FIG. 2 is a perspective view of the Surgeon's Console 16. The Surgeon'sConsole 16 includes a left eye display 32 and a right eye display 34 forpresenting the Surgeon 18 with a coordinated stereo view of the surgicalsite that enables depth perception. The Console 16 further includes oneor more input control devices 36, which in turn cause the Patient SideCart 22 (shown in FIG. 1A) to manipulate one or more tools. The inputcontrol devices 36 can provide the same degrees of freedom as theirassociated tools 26 (shown in FIG. 1A) so as to provide the Surgeon withtelepresence, or the perception that the input control devices 36 areintegral with the tools 26 so that the Surgeon has a strong sense ofdirectly controlling the tools 26. To this end, position, force, andtactile feedback sensors (not shown) may be employed to transmitposition, force, and tactile sensations from the tools 26 back to theSurgeon's hands through the input control devices 36.

The Surgeon's Console 16 is usually located in the same room as thepatient so that the Surgeon may directly monitor the procedure, bephysically present if necessary, and speak to an Assistant directlyrather than over the telephone or other communication medium. However,the Surgeon can be located in a different room, a completely differentbuilding, or other remote location from the Patient allowing for remotesurgical procedures.

FIG. 3 is a perspective view of the Electronics Cart 24. The ElectronicsCart 24 can be coupled with the endoscope 28 and can include a processorto process captured images for subsequent display, such as to a Surgeonon the Surgeon's Console, or on another suitable display located locallyand/or remotely. For example, where a stereoscopic endoscope is used,the Electronics Cart 24 can process the captured images so as to presentthe Surgeon with coordinated stereo images of the surgical site. Suchcoordination can include alignment between the opposing images and caninclude adjusting the stereo working distance of the stereoscopicendoscope. As another example, image processing can include the use ofpreviously determined camera calibration parameters so as to compensatefor imaging errors of the image capture device, such as opticalaberrations.

FIG. 4 shows a Patient Side Cart 22 having a plurality of manipulatorarms, each supporting a surgical instrument or tool 26 at a distal endof the manipulator arm. The Patient Side Cart 22 shown includes fourmanipulator arms 100 which can be used to support either a surgical tool26 or an imaging device 28, such as a stereoscopic endoscope used forthe capture of images of the site of the procedure. Manipulation isprovided by the robotic manipulator arms 100 having a number of roboticjoints. The imaging device 28 and the surgical tools 26 can bepositioned and manipulated through incisions in the patient so that akinematic remote center is maintained at the incision so as to minimizethe size of the incision. Images of the surgical site can include imagesof the distal ends of the surgical instruments or tools 26 when they arepositioned within the field-of-view of the imaging device 28.

Regarding surgical tool 26, a variety of alternative robotic surgicaltools or instruments of different types and differing end effectors maybe used, with the instruments of at least some of the manipulators beingremoved and replaced during a surgical procedure. Several of these endeffectors, including DeBakey Forceps, microforceps, Potts scissors, andclip applier include first and second end effector elements which pivotrelative to each other so as to define a pair of end effector jaws.Other end effectors, including scalpel and electrocautery probe have asingle end effector element. For instruments having end effector jaws,the jaws will often be actuated by squeezing the grip members of handle.Single end effector instruments may also be actuated by gripping of thegrip members, for example, so as to energize an electrocautery probe.

The elongate shaft of instrument 26 allow the end effectors and thedistal end of the shaft to be inserted distally into a surgical worksitethrough a minimally invasive aperture, often through an abdominal wallor the like. The surgical worksite may be insufflated, and movement ofthe end effectors within the patient will often be effected, at least inpart, by pivoting of the instrument 26 about the location at which theshaft passes through the minimally invasive aperture. In other words,manipulators 100 will move the proximal housing of the instrumentoutside the patient so that shaft extends through a minimally invasiveaperture location so as to help provide a desired movement of endeffector. Hence, manipulators 100 will often undergo significantmovement outside patient P during a surgical procedure.

Exemplary manipulator arms in accordance with many embodiments of thepresent invention can be understood with reference to FIGS. 5A-12C. Asdescribed above, a manipulator arm generally supports a distalinstrument or surgical tool and effects movements of the instrumentrelative to a base. As a number of different instruments havingdiffering end effectors may be sequentially mounted on each manipulatorduring a surgical procedure (typically with the help of a surgicalassistant), a distal instrument holder will preferably allow rapidremoval and replacement of the mounted instrument or tool. As can beunderstood with reference to FIG. 4, manipulators are proximally mountedto a base of the patient side cart. Typically, the manipulator armincludes a plurality of linkages and associated joints extending betweenthe base and the distal instrument holder. In one aspect, an exemplarymanipulator includes a plurality of joints having redundant degrees offreedom such that the joints of the manipulator arm can be driven into arange of differing configurations for a given end effector position.This may be the case for any of the embodiments of manipulator armsdisclosed herein.

In many embodiments, such as the example in FIG. 5A, the manipulator armincludes a proximal revolute joint J1 that rotates about a first jointaxis so as to revolve the manipulator arm distal of the joint about thejoint axis. Revolute joint J1 is mounted directly to the base or may bemounted to one or more movable linkages or joints. The joints of themanipulator, in combination, have redundant degrees of freedom such thatthe joints of the manipulator arm can be driven into a range ofdiffering configurations for a given end effector position. For example,the manipulator arm of FIGS. 5A-5D may be maneuvered into differingconfigurations while the distal member 511 (such as a cannula throughwhich the tool 512 or instrument shaft extends) supported within theinstrument holder 510 maintains a particular state and may include agiven position or velocity of the end effector. Distal member 511 istypically a cannula through which the tool shaft 512 extends, and theinstrument holder 510 is typically a carriage (shown as a brick-likestructure that translates on a spar) to which the instrument attachesbefore extending through the cannula 511 into the body of the patientthrough the minimally invasive aperture.

Describing the individual links of the example manipulator arm 500 ofFIGS. 5A-5D along with the axes of rotation of the joints connecting thelinks as illustrated in FIG. 5A-5D, a first link 504 extends distallyfrom a pivotal joint J2 which pivots about its joint axis and is coupledto revolute joint J1 which rotates about its joint axis. Many of theremainder of the joints can be identified by their associated rotationalaxes, as shown in FIG. 5A. For example, a distal end of first link 504is coupled to a proximal end of a second link 506 at a pivotal joint J3that pivots about its pivotal axis, and a proximal end of a third link508 is coupled to the distal end of the second link 506 at a pivotaljoint J4 that pivots about its axis, as shown. The distal end of thethird link 508 is coupled to instrument holder 510 at pivotal joint J5.Typically, the pivotal axes of each of joints J2, J3, J4, and J5 aresubstantially parallel and the linkages appear “stacked” when positionednext to one another, as shown in FIG. 5D, so as to provide a reducedwidth w of the manipulator arm and improve patient clearance duringmaneuvering of the manipulator assembly. In certain embodiments, theinstrument holder includes additional joints, such as a prismatic jointJ6 that facilitates axial movement of instrument 306 through theminimally invasive aperture and facilitates attachment of the instrumentholder to a cannula through which the instrument is slidably inserted.

In this example manipulator arm, the distal member or cannula 511through which the tool 512 extends may include additional degrees offreedom distal of instrument holder 510. Actuation of the degrees offreedom of the instrument will often be driven by motors of themanipulator, and alternative embodiments may separate the instrumentfrom the supporting manipulator structure at a quickly detachableinstrument holder/instrument interface so that one or more joints shownhere as being on the instrument are instead on the interface, or viceversa. In some embodiments, cannula 511 includes a rotational joint J8(not shown) near or proximal of the insertion point of the tool tip orthe pivot point PP, which generally is disposed at the site of aminimally invasive aperture. A distal wrist of the instrument allowspivotal motion of an end effector of surgical tool 512 about instrumentjoints axes of one or more joints at the instrument wrist. An anglebetween end effector jaw elements may be controlled independently of theend effector location and orientation.

The range of motion of an example manipulator assembly can beappreciated by referring to the examples in FIGS. 6A-6C. During asurgical procedure, the manipulator arm can be maneuvered into a pitchforward configuration, as shown in FIG. 6A, or into a pitch backconfiguration, as shown in FIG. 6B, as needed to access particularpatient tissues within a surgical workspace. A typical manipulatorassembly includes an end effector that can pitch forwards and backwardsabout an axis by at least ±60 degrees, preferably by about ±75 degrees,and can also yaw about an axis by ±80 degrees. Although this aspectallows for increased maneuverability of the end effector with theassembly, there may be configurations in which movement of the endeffector may be limited, particularly when the manipulator arm is in thefull pitch forward or full pitch back configuration as in FIGS. 6A and6B. In this embodiment, the manipulator arm has a Range of Motion (ROM)of (±75 deg) for the outer pitch, and (±300 degrees) for the outer yawjoints, respectively. In some embodiments, the ROM may be increased forthe outer pitch to provide a ROM larger than (±90 deg) in which case the“cone of silence” could be made to disappear entirely, althoughgenerally the inner sphere associated with insertion limitations wouldremain. It is appreciated the manipulator may be configured to haveincreased or decreased ROM, that the above noted ROMs are provided forillustrative purposed, and further that the invention is not limited tothe ROMs described herein.

FIG. 6C graphically represents the overall range of motion and workspaceof the tool tip of the exemplary manipulator of FIGS. 5A-5B. Althoughthe workspace is shown as hemisphere, it may also be represented as asphere depending on the range of motion and configuration of one or morerevolute joints of the manipulator, such as joint J1. As shown, thehemisphere in FIG. 6C includes a central, small spherical void as wellas two conical voids. The voids represent the areas in which movement ofthe tool tip may be impossible due to mechanical constraints orunfeasible due to extremely high joint velocities that make movement ofthe end effector difficult or slow. For these reasons, the conical voidare referred to as the “cone of silence.” In some embodiments, themanipulator arm may reach a singularity at a point within the cone.Since movement of the manipulator within or near the cone of silence maybe impaired, it can be difficult to move the manipulator arm away fromthe cone of silence without manually moving one or more links of themanipulator to reconfigure the linkages and joints of the manipulator,which often requires an alternative operating mode and delays thesurgical procedure.

Movement of the instrument shaft into or near these conical portionstypically occurs when the angle between distal linkages in themanipulator is relatively small. Such configurations can be avoided byreconfiguring the manipulator to increase the angles between linkages(so that the linkages are moved into a more orthogonal position relativeto each other). For example, in the configurations shown in FIGS. 6A and6B, when the angle between the distal most link and the instrumentholder (angle a) becomes relatively small, movement of the manipulatorbecomes more difficult. Depending on the range of joint movements in theremaining joints in various embodiments, when the angle between certainlinkages decreases, movement of the manipulator may be inhibited and insome cases, the manipulator arm may no longer be redundant. Amanipulator configuration in which the instrument shaft nears theseconical portions, or in which the angles between linkages are relativelylow is said to be “poorly conditioned” such that maneuverability anddexterity of the manipulator arm is limited. It is desirable that themanipulator be “well conditioned” so as to maintain dexterity and rangeof movement. In one aspect, the present invention allows a user to avoidmovement of the instrument shaft near the above described conicalportions by simply entering a command to reconfigure the manipulator asdesired, even during movement of the end effector in a surgicalprocedure. This aspect is particularly useful should the manipulator,for whatever reason, become “poorly conditioned.”

While the embodiments described are utilized in the present invention,some embodiments may include additional joints, which may also be usedto improve dexterity and the conditioning of the manipulator arm. Forexample, an exemplary manipulator may include a revolute joint and/orlinkage proximal of joint J1 which can be used to revolve themanipulator arm of FIG. 5A, and its associated cone of silence, about anaxis of the revolute joint so as to reduce or eliminate the cone ofsilence. In another embodiment, the exemplary manipulator may alsoinclude a distal pivotal joint that pivots the instrument holder aboutan axis substantially perpendicular to joint J5, thereby offsetting thetool tip so as to further reduce the cone of silence and improve therange of movement of the surgical tool. In still another embodiment, aproximal joint of the manipulator arm, such as J1, may be movablymounted on the base, so as to move or shift the cone of silence asneeded and improve the range of motion of the manipulator tool tip. Theuse and advantages of such additional joints can be understood byreferring to FIGS. 7A-12C, which illustrate examples of such joints,which may each be used independent of one another or used incombination, in any of the exemplary manipulator arms described herein.

FIGS. 7A-7B illustrate an additional redundant joint for use withexemplary manipulator arms—a first joint coupling a proximal portion ofthe manipulator arm to the base. The first joint is a proximal revolutejoint J1′ that revolves the manipulator arm about a joint axis of jointJ1′. The proximal revolute J1′ includes a link 501 that offsets joint J1from the proximal revolute J1′ by a pre-determined distance or angle.The link 501 can be a curved linkage, as shown in FIG. 7A, or a linearor angled linkage, as shown in FIG. 7B. Typically, the joint axis of thejoint J1′ is aligned with the remote center RC or insertion point of thetool tip, as shown in each of FIG. 7A. In an exemplary embodiment, thejoint axis of joint J1′ passes through the remote center, as does eachother revolute joint axis in the manipulator arm, to prevent motion atthe body wall and can therefore be moved during surgery. The axis ofjoint J1′ is coupled to a proximal portion of the arm so it can be usedto change the position and orientation of the back of the arm. Ingeneral, redundant axes, such as this, allow the instrument tip tofollow the surgeon's commands while simultaneously avoiding collisionswith other arms or patient anatomy. In one aspect, the proximal revoluteJ1′ is used solely to change the mounting angle of the manipulator withrespect to the floor. This angle is important in order to 1) avoidcollisions with external patient anatomy and 2) reach anatomy inside thebody. Typically, the angle a between the proximal link of themanipulator attached to the proximal revolute joint J1′ and the axis ofthe proximal revolute is about 15 degrees.

FIG. 7B illustrates the relationship of the proximal revolute joint J1′and its associated joint axis and the cone of silence in an exemplarymanipulator arm. The joint axis of the proximal revolute joint J1′ maypass through the cone of silence or may be completely outside of thecone of silence. By revolving the manipulator arm about the axis of theproximal revolute J1′, the cone of silence can be reduced (in anembodiment where the joint J1′ axis passes through the cone of silence),or can be effectively eliminated (in an embodiment where the proximalrevolute joint axis extends completely outside the cone of silence). Thedistance and angle of the link 501 determines the position of the jointJ1′ axis relative to the cone of silence.

FIGS. 8-9 illustrates another type of redundant joint for use withexemplary manipulator arms, a distal revolute joint J7 coupling theinstrument holder 510 to a distal link of the manipulator arm 508. Thedistal revolute joint J7 allows the system to laterally pivot or twistthe instrument holder 510 about the joint axis, which typically passesthrough the remote center or insertion point. Ideally, the revolutejoint is located distally on the arm and is therefore particularly wellsuited to moving the orientation of the insertion axis. The addition ofthis redundant axis allows the manipulator to assume multiple positionsfor any single instrument tip position. In general, redundant axes, suchas this, allow the instrument tip to follow the surgeon's commands whilesimultaneously avoiding collisions with other arms or patient anatomy.Because the distal revolute joint J7 has the ability to move theinsertion axis closer to the yaw axis, it is able to increase the rangeof motion when the manipulator arm is in a pitch back position. FIGS.10A-10C show the sequential movement of joint J7 and how movement ofjoint J7 shifts the insertion axis of tool tip from side to side.

In another aspect, any of the systems described herein may utilize auser input device to drive one or more joints and reconfigure one ormore joints of the manipulator arm within a null-space to effect adesired reconfiguration for a variety of reasons. In an embodimenthaving one or both of a user input for commanded reconfiguration or amode as described above, the system may utilize the constraintsdescribed above during movement to effect commanded manipulationmovement and suspend application of the constraints during areconfiguration movement or while in the clutch mode. When thereconfiguration movement is completed or the manipulator arm is switchedout of clutch mode, the system applies the position-based constraintsaccording to the reconfigured location of the manipulator arm. In otherembodiments, the constraints may define multiple positional paths ofmovement such that the constraints associated with the closest pathwithin the Cartesian-coordinate space can be selected. These aspectsallow the system to provide the desired movement of the one or morejoints of the manipulator arm after being reconfigured, by a drivenreconfiguration or a manual reconfiguration while in a clutch mode.

One advantage of using an additional redundant joint, such as distalrevolute joint J7, is that it may be used to reduce the patientclearance cone, which is the swept volume of the distal portion of themanipulator arm proximal of the insertion point which must clear thepatient to avoid collision between the patient and the instrument holderor distal linkages of the manipulator arm. FIG. 11A illustrates thepatient clearance cone of the proximal portion of the manipulator armwhile the angular displacement of the distal revolute joint remains at0°. FIG. 11B illustrates the reduced patient clearance cone of theproximal portion of the manipulator arm while the distal revolute jointis shown having an angular displacement of 90° about its axis. Thus, inprocedures having minimal patient clearance near the insertion point,use of the joint J7 in accordance with the present invention may provideadditional clearance while maintaining the remote center location or theposition of the end effector as desired.

FIGS. 12A-12C illustrate another type of redundant joint for use withexemplary manipulator arms, a proximal joint that translates or revolvesthe manipulator arm about an axis. In many embodiments, this proximaltranslatable joint translates a proximal joint of the manipulator, suchas joint J1 or J1′, along a path so as to reduce or eliminate the coneof silence by shifting or rotating the range of motion of themanipulator arm to provide for better conditioning and improvedmaneuverability of the manipulator arm. The translatable joint mayinclude a circular path, such as shown in joint J1″ in FIGS. 12A-12D, ormay include a semi-circular or arcuate path, such as shown in FIGS.13A-13C. Generally, the joint revolves the manipulator arm about an axisof the translatable joint that intersects with the remote center RCabout which the shaft of the tool 512 extending through cannula 511pivots. Although in the embodiment shown in FIGS. 12A-12C, the axis ofJ1″ is a vertical axis, it is appreciated that the axis of J1″ may behorizontal or disposed at various angles of inclination.

In certain embodiments, the manipulator arm 500 may include any or allof a proximal or distal revolute joint, a proximal translatable jointand a parallelogram configuration of the distal linkages. Use of any orall of these features provide additional redundant degrees of freedomand facilitate reconfiguration in accordance with the present inventionso as to provide for a better “conditioned” manipulator assembly byincreasing the angles between linkages thereby improving the dexterityand motion of the manipulator. The increased flexibility of thisexemplary manipulator can also be used to optimize the kinematics of themanipulator linkage so as to avoid joint limits, singularities, and thelike.

In certain aspects, the joint movements of the manipulator arecontrolled by driving one or more joints by a controller using motors ofthe system, the joints being driven according to coordinated and jointmovements calculated by a processor of the controller. Mathematically,the controller may perform at least some of the calculations of thejoint commands using vectors and/or matrices, some of which may haveelements corresponding to configurations or velocities of the joints.The range of alternative joint configurations available to the processormay be conceptualized as a joint space. The joint space may, forexample, have as many dimensions as the manipulator has degrees offreedom, and a particular configuration of the manipulator may representa particular point in the joint space, with each coordinatecorresponding to a joint state of an associated joint of themanipulator.

In one aspect, the system includes a controller in which a commandedposition and velocity of a feature in the work-space, denoted here asits Cartesian space, are inputs. The feature may be any feature on themanipulator or off the manipulator which can be used as a control frameto be articulated using control inputs. An example of a feature on themanipulator, used in many examples described herein, would be thetool-tip. Another example of a feature on the manipulator would be aphysical feature which is not on the tool-tip, but is a part of themanipulator, such as a pin or a painted pattern. An example of a featureoff the manipulator would be a reference point in empty space which isexactly a certain distance and angle away from the tool-tip. Anotherexample of a feature off the manipulator would be a target tissue whoseposition relative to the manipulator can be established. In all thesecases, the end effector is associated with an imaginary control framewhich is to be articulated using control inputs. However, in thefollowing, the “end effector” and the “tool tip” are used synonymously.Although generally, there is no closed form relationship which maps adesired Cartesian space end effector position to an equivalentjoint-space position, there is generally a closed form relationshipbetween the Cartesian space end effector and joint-space velocities. Thekinematic Jacobian is the matrix of partial derivatives of Cartesianspace position elements of the end effector with respect to joint spaceposition elements. In this way, the kinematic Jacobian captures thekinematic relationship between the end effector and the joints. In otherwords, the kinematic Jacobian captures the effect of joint motion on theend effector. The kinematic Jacobian (J) can be used to map joint-spacevelocities (dq/dt) to Cartesian space end effector velocities (dx/dt)using the relationship below:

dx/dt=Jdq/dt

Thus, even when there is no closed-form mapping between input and outputpositions, mappings of the velocities can iteratively be used, such asin a Jacobian-based controller to implement a movement of themanipulator from a commanded user input, however a variety ofimplementations can be used. Although many embodiments include aJacobian-based controller, some implementations may use a variety ofcontrollers that may be configured to access the Jacobian of themanipulator arm to provide any of the features described herein.

One such implementation is described in simplified terms below. Thecommanded joint position is used to calculate the Jacobian (J). Duringeach time step (Δt) a Cartesian space velocity (dx/dt) is calculated toperform the desired move (dx_(des)/dt) and to correct for built updeviation (Δx) from the desired Cartesian space position. This Cartesianspace velocity is then converted into a joint-space velocity (dq/dt)using the pseudo-inverse of the Jacobian (j^(#)). The resultingjoint-space commanded velocity is then integrated to produce joint-spacecommanded position (q). These relationships are listed below:

dx/dt=dx _(des) /dt+kΔx  (1)

dq/dt=J ^(#) dx/dt  (2)

q _(i) =q _(i−1) +dq/dt Δt  (3)

The pseudo-inverse of the Jacobian (J) directly maps the desired tooltip motion (and, in some cases, a remote center of pivotal tool motion)into the joint velocity space. If the manipulator being used has moreuseful joint axes than tool tip degrees of freedom (e.g. up to sixdegrees of freedom), then the manipulator is said to be redundant. Forexample, when a remote center of tool motion is in use, the manipulatorshould have an additional 3 joint axes for the 3 degrees of freedomassociated with location of the remote center. A redundant manipulator'sJacobian includes a “null-space” having a dimension of at least one. Inthis context, the “null-space” of the Jacobian (N(J)) is the space ofjoint velocities which instantaneously achieves no tool tip motion (andwhen a remote center is used, no movement of the pivotal pointlocation); and “null-motion” is the combination, trajectory or path ofjoint positions which also produces no instantaneous movement of thetool tip and/or location of the remote center. Incorporating orinjecting the calculated null-space velocities into the control systemof the manipulator to achieve the desired reconfiguration of themanipulator (including any reconfigurations described herein) changesabove equation (2) to the following:

dq/dt=dq _(perp) /dt+dq _(null) /dt  (4)

dq _(perp) /dt=J ^(#) dx/dt  (5)

dq _(null) /dt=(1−H ^(#) J)z=V _(n) V _(n) ^(T) z=V _(n)α  (6)

The joint velocity according to Equation (4) has two components: thefirst being the null-perpendicular-space component, the “purest” jointvelocity (shortest vector length) which produces the desired tool tipmotion (and when the remote center is used, the desired remote centermotion); and the second being the null-space component. Equations (2)and (5) show that without a null-space component, the same equation isachieved. Equation (6) starts with a traditional form for the null-spacecomponent on the left, and on the far right side, shows the form used inan exemplary system, wherein (V_(n)) is the set of orthonormal basisvectors for the null-space, and (α) are the coefficients for blendingthose basis vectors. In some embodiments, α is determined by controlparameters, variables or setting, such as by use of knobs or othercontrol means, to shape or control the motion within the null-space asdesired.

FIG. 13A graphically illustrates the relationship between the null-spaceof the Jacobian and the null-perpendicular-space of the Jacobian. FIG.14 shows a two-dimensional schematic showing the null-space along thehorizontal axis, and the null-perpendicular-space along the verticalaxis, the two axes being orthogonal to one another. The diagonal vectorrepresents the sum of a velocity vector in the null-space and a velocityvector in the null-perpendicular-space, which is representative ofEquation (4) above.

FIG. 13B graphically illustrates the relationship between the null-spaceand the null-motion manifold within a four-dimensional joint space,shown as the “null-motion manifold.” Each arrow (q1, q2, q3, and q4)representing a principal joint axis. The closed curve represents anull-motion manifold which is a set of joint-space positions whichinstantaneously achieves the same end effector position. For a givenpoint A on the curve, since the null-space is a space of jointvelocities which instantaneously produce no movement of the endeffector, the null-space is parallel to the tangent of the null-motionmanifold at point A.

FIG. 14 graphically illustrates the two-dimensional subspace of thejoint-space of an exemplary manipulator arm. The horizontal and verticalaxes represent the movement of two joints having independent jointmovement, in particular, movement of joint affecting a pitch of aninstrument holder of the manipulator arm (horizontal-axis) versusmovement of a distal revolute joint that pivots the instrument holderlaterally in either direction from a plane through which a proximalportion of the manipulator arm extends (vertical-axis). The far rightside of the subspace represents the forward pitch limit of the pitchjoint and the far left side represents the backward pitch limit of thepitch joint. The defined pathways near, curves A, B and C, D, near theforward and backward pitch limits of the pitch joint, respectively,illustrate joint-states of joint movement within a null-space of theJacobian of the joints of the manipulator arm. For example, for a givenend effector state, a controller can move the lateral pivot joint andthe pitch joint along each of curves A, B, C and D to increase the rangeof joint space orthogonal to curves A, B, C and D while maintaining thedesired state of the end effector.

The curved lines, A, B, C shown in FIG. 14 indicate joint-space valueswithin the joint-space that lead to a substantially constantCartesian-space pitch. Each curve is a null-motion manifold, asdescribed in FIG. 13B. During operation of the particular manipulatorarm represented by the joint-space in FIG. 14, a greater number of pathcurves can be traversed in a forward pitch by approaching the horizontalaxis (e.g. angular displacement of the lateral pivotal joint approacheszero degrees). Alternatively, a greater number of path curves can betraversed in a backward pitch by approaching the upper and lower cornersof the joint-space (e.g. angular displacement of the lateral pivotaljoint approaches its ±extrema).

As can be seen in FIG. 14, the Cartersian-coordinate joint space of therepresented manipulator arm has four corners. In general, for the jointsof the manipulator arm to access the four corners, a controllereffecting movement of the joints points toward the corners. In oneaspect, a controller calculates movement within a null-space of theJacobian to move the joints along one or more paths in a joint-space,such as the curves within the joint-space shown in FIG. 14, to improveaccess of the manipulator arm to the far corners of theCartesian-coordinate space. In one approach, a potential field isdefined within a joint sub-space of the manipulator arm to move thejoints along family of curves are used to be able to reach the edges andcorners of the joint space, or joint limits in various jointcombinations, and in particular the far reaches of theCartesian-coordinate space. Cartesian-space reaches represented by thepitch joint and the lateral pivotal joint ranges within the joint spaceare shown in FIG. 14.

One way to define the potential field, which is shown in FIG. 14, is asfollows:

C=½(q _(pitch) −q _(pitch-setpoint))²

z=(dC/dt)^(T) =∂C/∂q*dq/dt=(q _(pitch) −q _(pitch-setpoint))*dq/dt

where z is then used in equation (6) above.

Alternatively, in certain aspects, an augmented Jacobian thatincorporates a potential function gradient and is applied to theCartesian Space end effector velocities may be used. The augmentation ofthe Jacobian calculates the joint velocities as desired. It isunderstood that in referring to calculating joint movements using theJacobian, such calculations may include the augmented Jacobian approach.In accordance with the augmented Jacobian approach, the followingequations may be used, although it is appreciated that column vectorsmay be used:

dx/dt=J*dq/dt

y=h(q)

dy/dt=∂h/∂q*dq/dt

[dx/dt ^(T) dy/dt ^(T)]^(T) =[J ^(T) ∂h/∂q ^(T)]^(T) *dq/dt

d(x;y)/dt=[J;h′]*dq/dt

dq/dt=[J;h′] ^(#) d(x;y)/dt

In one example, the system is configured to set y=h(q) the complexnetwork of potential field functions. The dy/dt=∂h/∂q*dq/dt. dy/dt and∂h/∂q and dy/dt can be dictated as desired based on the potential fieldfunctions, and the augmented equation would produce the combined desiredresult of both driving the end effector and tracking the paths in jointspace.

The controller may move the joints orthogonal to paths A, B, C and Dusing a pseudo-inverse of the Jacobian so as to effect movement of thejoints within a null-perpendicular space according to a commanded endeffector displacing movement to effect a desired end effectormanipulation movement. As the pitch of the pitch joint moves along thehorizontal-axis during commanded end effector movement, the systemdetermines movements of the joints positions within a null-space toincrease the range of joint space. As shown in FIG. 14 for example, asmovement of the pitch joint moves toward the backward limit, the systemmay determine and effect displacing movement of the lateral pivot jointwithin the null-space along the nearest curve (see arrow along curve Bin FIG. 14) so as to increase the range of joint motion within thenull-perpendicular space by increasing the orthogonal distance betweenthe curved path and the limits of the manipulator joint space. Forexample, in joint space shown in FIG. 14, as the pitch joint movestoward the forward pitch joint limit, the system may determine andeffect movement of the lateral pivot joint toward a non-displacedposition so as to increase the range of motion within thenull-perpendicular space by increasing the orthogonal distance betweencurved paths (C and D) and the pitch joint forward limit. A virtualpotential field space may be used in the joint space to allow fordetermination of a virtual force that can be used to determine jointvelocities to effect the desired movement of the joints within the jointspace.

In certain embodiments, the manipulator arm uses a parallelogram linkagein which joints J3, J4 and J5 are configured with interrelated movementto maintain the parallelogram formed by joints J3, J4, J5 and pivotpoint PP (see for example FIG. 5A). Due to this interrelated movement,the pitch of the instrument shaft may be determined by the state of apitch joint (e.g. J3). Movement of the pitch joint, such as joint J3 inFIG. 5A, changes the pitch of the insertion axis from a pitch forwardposition (see FIG. 6A) to a pitch back position (see FIG. 6B). Invarious other embodiments, the pitch joint may include one or morejoints of a manipulator arm the movement of which determines the pitchof the instrument shaft. Movement of the distal revolute joint, such asdistal revolute joint J7 supporting the instrument holder 510 andassociated cannula 511, pivots or twists the instrument shaft extendingthrough instrument holder 510 laterally relative to a plane throughwhich the portion of the manipulator arm proximal of joint J7 extends.The sub-space of the manipulator joint space illustrates the range ofpossible combinations of joint states for the pitch joint, J3, and therevolute joint, J7. Although in this embodiment, the positionalconstraints are defined within a subspace of the joint space defined bythe pitch joint and the distal revolute joint described above, it isappreciated that the subspace may be defined by various other joints orby three or more joints.

In the embodiment shown, the movement along the curved paths includesrelative movement of the distal revolute joint and pitch joint so thatmovement of the pitch joint to an increased pitch back positioncorresponds to increased rotational displacement of the revolute joint,and movement of the pitch joint to a pitch forward position correspondsto minimal or zero displacement of the distal revolute joint. As theouter pitch joint is pitched back, the tool tip on the instrument shaftmoves forward. If the outer pitch joint reaches its limit in thepitch-back position, forward movement of a tool tip on the end of theinstrument shaft 512 can still be achieved by movement of the distalrevolute joint J7. It may be useful however, to initiate movement of thedistal revolute joint, J7, as the outer pitch joint J3 approaches itslimit in the pitch-back position. Similarly, in the pitch-forwarddirection, which causes tool tip motion in the backwards direction, themost backward tool tip positioning can be obtained when the movement ofthe distal revolute joint is minimal, which is at zero angulardisplacement of the distal revolute joint.

In one aspect, at any point in time, being on any of the paths or curvescoincides with meeting a one-dimensional constraint requiring aone-dimensional null-space. This two-dimensional subspace of manipulatorjoint space can be used to direct the movement of the manipulator arm tothe desired positional path by creating an attractive potential fieldwhich tends to “pull” or direct the position X of the subject jointstates toward or along the defined paths, typically along the path. Thesystem may be configured so that the access facilitating movement of thejoints causes the specified joints to move along the defined pathsegments or may use various magnitudes of attraction within thepotential field to cause the joints to along the defined path so as toprovide increased range of movement within the joint space of at leastone of the joints for a given state of the joints of the manipulator.

In one approach, this is accomplished by generating a potential field injoint-space, such that high potentials represent shorter distancesbetween the X (e.g. the current or calculated manipulator position) andthe positional constraint (e.g., the network of paths), and lowerpotentials represent larger distances. The null-space coefficients (a)are then calculated to descend down the negative gradient of thepotential field, preferably to the greatest extent possible. In someembodiments, a potential associated with each path (e.g., b′ and c′) isdetermined from a distance between the calculated position of the one ormore manipulator joints and the defined paths. In response to thecalculated attractive force of the artificial potential field on thecurrent joint positions, the system calculates movement of one or morejoints of the manipulator arm within the null-space.

While the constraints may be defined as three segments A, B and C withina subspace defined by a distal revolute joint and an outer pitch jointas shown in FIGS. 14A-14C, it is appreciated that the above notedadvantages are associated with certain kinematics of a given manipulatorarm. Thus, as the kinematics may differ between manipulator arms, so maythe desired joint movements and the configuration constraints differbetween manipulator arms. For example, depending on the design of amanipulator arm, it may be useful to define the subspace in which thepositional constraints are defined by two or more other joints of themanipulator arm. For example, assuming an N-dimensional null-space, anetwork of N-dimensional manifolds in any dimensional subspace of thefull joint space may be defined. In a first example, in a one or moredimensional null-space, a network of one-dimensional curves or linesegments may be defined in the entire joint space or in any subspace oftherein. Attractive potentials or velocities may then be calculated andprojected onto the null-space to determine the access facilitatingmovement so that a position of the one or more joints corresponds to thedefined paths that provide increased range of joint movement, therebyfacilitating access to the edges of joints limits of the joint space forone or more joints. In a second example, assuming a null-space of two ormore dimensions, a network of two-dimensional surfaces may be defined inthe entire joint space or in any subspace therein. Again, attractivepotentials or velocities may then be calculated and projected on thenull-space as described above. In both examples, the approach causes themanipulator to follow the network of paths, or surfaces rather, toproduce the desired movement. In a third example, assuming a null-spaceof one dimension, a network of two-dimensional surfaces could still bedefined in the entire joint space or in a subspace thereof, however,mapping velocities or attractive potentials onto the null-space mayprovide limited capability in following the network surfaces.

In certain aspects, the approach includes defining positionalconstraints, such as in a joint-space or in the Cartesian-coordinatespace of the tool tip (or some other portion of the manipulator and mayinclude a remote center, such as found in either a hardware or softwarecenter system). For a manipulator with n-DOF of redundancy, ann-dimensional null-space of up to n constraints can be satisfiedsimultaneously). For a case having one-dimensional constraints, this mayinclude a set of piece-wise continuous constraints. One or more paths(e.g. series of curves) may be used to define a network of paths ineither the joint-space of the Cartesian-coordinate space. The network ofpaths may be either static or may be dynamically redefined during thecourse of surgery. A static network path may be defined at start-up ormay be selected by a user or the system from a plurality of staticnetwork paths, while a dynamic network path may be dynamically redefinedby the system, or by a user, during the course of surgery.

Once the curve paths for facilitating access to the edges ofCartesian-space is determined, the movement of the joints of themanipulator arm is calculated so that the position of the one or morejoints tracks the curved paths so as to provide the desired movement ofthe one or more joints. In some embodiments, the joints of themanipulator arm tracks the curved paths based on a virtual or artificialpotential field generated for each segment of that path to attract themanipulator to the path. The movement resulting from the calculatedpotential may then be projected onto the null-space for calculation ofnull-space coefficient to provide joint velocities that provide thedesired range of joint motion within the Cartesian-space.

FIGS. 15-16 illustrate methods of reconfiguring a manipulator assemblyof a robotic surgical system in accordance with many embodiments of thepresent invention. FIG. 15 shows a simplified schematic of the requiredblocks need to implement the general algorithms to control the patientside cart joint states, in relation to the equations discussed above.According to the method of FIG. 15, the system: calculates the forwardkinematics of the manipulator arm; then calculates dx/dt using Equation(1), calculates dq_(perp)/dt using Equation (5), then calculatesdq_(null)/dt from z which may depend on dq_(perp)/dt and the Jacobianusing Equation (6). From the calculated dq_(perp)/dt and dq_(null)/dtthe system then calculates dq/dt and q using Equations (4) and (3),respectively, thereby providing the movement by which the controller caneffect the desired reconfiguration of the manipulator while maintainingthe desired state of the end effector and/or location of the remotecenter.

FIG. 16 shows a block diagram of an exemplary embodiment of the system.In response to a manipulation command, which commands a desired tool tipstate, a processor of the system determines the velocities of the tooltip and the states of the joints from which the dq_(perp)/dt iscalculated. To provide an increased range of joint movement for one ormore joints of the manipulator arm, the system determined position-basedconstraints within the subspace of the joints for which controlledmovement is desired, such as a series of curved paths representing jointmovement within the null-space, the curved paths defined to increase anorthogonal distance between the curved paths and the limits or edges ofthe joints space, the orthogonal distance corresponding tonull-perpendicular movement within the joint space. The dq_(null)/dt isthen calculated so as to move the joints within the null-space along thepositional constraint, such as through the use of an attractivepotential field calculated along a curved path in the joint space, whichmay be added to the dq_(perp)/dt to calculate dq/dt so as to drive thejoint(s) of the system and effect the desired movement (or state) of theend effector while providing an increased range of movement of the oneor more joints within the null-perpendicular space as desired.

FIG. 17 shows a flow chart of an example method in accordance withaspect of the present invention. The method includes: determining a setof position-based constraints within a joint space that correspond to adesired range of joint movement of one or more joints; determine apotential between the position of the one or more joints and theconstraints within an artificial potential field; calculating a movementof the joint(s) within a null-space using the determined potential toprovide the increase range of joint movement of the one or more jointswithin the null-perpendicular space; and driving the joints according tothe calculated movement to effect the desired movement of the one ormore joints while maintaining and/or increasing the range of jointmovement of the one or more joints.

While the exemplary embodiments have been described in some detail forclarity of understanding and by way of example, a variety ofadaptations, modifications, and changes will be obvious to those ofskill in the art. Hence, the scope of the present invention is limitedsolely by the appended claims.

What is claimed is:
 1. A robotic method comprising: providing amanipulator arm including a movable distal surgical end effector, aproximal portion coupled to a base, and a plurality of joints betweenthe end effector and the base, the plurality of joints having sufficientdegrees of freedom to allow a range of differing joint states for agiven end effector state; defining a position-based constraint of one ormore joints within a joint space of the plurality of joints for whichincreased range of movement is desired; receiving a manipulation commandto move the end effector with a desired end effector movement;calculating an end effector displacing movement of the one or morejoints to effect the desired end effector movement, wherein calculatingthe end effector displacing movement of the joints comprises calculatingjoint velocities within a null-perpendicular-space of a Jacobian; andcalculating a facilitating movement of a set of joint(s) of theplurality along the position-based constraint, the facilitating movementincreasing the available range of movement of the end effector, whereincalculating the facilitating movement comprises calculating jointvelocities of the one or more joints within a null-space of theJacobian, the null-space being orthogonal to the null-perpendicularspace; and driving the joints according to the calculated movements soas to effect the desired end effector movement while providing theincreased range of movement of the end effector.
 2. The method of claim1, wherein the positional constraint comprises one or more surfaceshaving at least one dimension, wherein the one or more surfaces aredefined within a subspace of the joint space defined by at least twojoints of the plurality of joints.
 3. The method of claim 2, wherein theat least two joints have independent joint states such that the subspacecomprises at least two dimensions.
 4. The method of claim 2, whereincalculating the facilitating movement comprises: defining an attractivepotential field based on a calculated position of the at least one jointwithin the joint space such that an decrease in potential drives thejoints; determining a potential between the calculated position and theone or more surfaces associated with the one or more joints; andcalculating the facilitating movement using the potential.
 5. The methodof claim 4, wherein the potential field is associated with movementalong the surface that corresponds to increased range of movement of oneor both of the at least two joints.
 6. The method of claim 4, whereincalculating the facilitating movement comprises: determining a movementof the plurality of joints within the joint space based on the potentialof the at least joint; and projecting the movement of the plurality ofjoints on a null-space of the Jacobian to determine joint velocities ofthe plurality of joints that extend the at least two joints toward theconstraint.
 7. The method of claim 2, wherein the at least two jointscomprise a first and a second joint, wherein movement of the first jointcontrols a pitch of a distal instrument shaft of the manipulator andmovement of the second joint pivots the instrument shaft laterallyrelative to a plane along which a portion of the manipulator armproximal of the second joint extends.
 8. The method of claim 6, whereina distal portion of the manipulator arm is coupled with an instrumentholder to releasably support a surgical instrument having an elongateshaft extending distally to the end effector, wherein the instrumentshaft pivots about a remote center during surgery.
 9. The method ofclaim 1, further comprising: driving at least one joint of the pluralityto effect a desired reconfiguration of the manipulator arm in responseto a user input reconfiguration command; calculating a reconfigurationmovement of one or more joints of the plurality in response to thedriving of the at least one joint so that the calculated movement incombination with driving of the at least one joint extends within thenull-space; modifying the position-based constraint in response to adetermined position of the one or more joints within the calculatedreconfiguration movement; driving the joints according to the calculatedmovements while driving the at least one joint according to the userinput reconfiguration command so as to maintain a desired state of theend effector while providing the increased range of movement of the oneor more joints.
 10. The method of claim 9, wherein modifying thepositioned-based constraint comprises translating a position ororientation of the constraint within the joint space based on thecalculated reconfiguration movement.
 11. The method of claim 9, whereinmodifying the position-based constraint comprises selecting one of a setof position-based constraints in response to the determined position ofthe one or more joints.
 12. The method of claim 9, wherein driving theat least one joint comprises manual articulation of the joint, whereinmovement of the manipulator arm is determined by a processor having atissue manipulation mode and a clutch mode, the processor in the tissuemanipulation mode calculating the joint movements to provide the desiredend effector movement in response to the end effector manipulationcommand, the processor in the clutch mode driving at least one otherjoint in response to the manual articulation of the at least one jointso as to maintain the desired state of the end effector, and whereinmodifying the position-based constraint occurs in response to thedetermined position of the one or more joints reconfigured within theclutch mode.
 13. A system comprising: a manipulator arm configured forrobotically moving a distal end effector relative to a proximal base,the manipulator arm having a plurality of joints between the distal endeffector and the proximal portion coupled to the base, the jointsproviding sufficient degrees of freedom to allow a range of joint statesfor a given state of the distal end effector; an input for receiving amanipulation command to move the end effector with a desired endeffector movement; and a processor coupling the input device to themanipulator arm, the processor configured to: calculate an end effectordisplacing movement of the joints in response to the manipulationcommand by calculating joint velocities within anull-perpendicular-space of a Jacobian; define a position-basedconstraint of one or more joints of the plurality within an associatedjoint space, the constraint corresponding to an increased range ofmovement of the one or more joints; calculate a facilitating movement ofthe one or more joints within a null-space of the Jacobian that movesthe one or more joints toward the constraint, the null-space beingorthogonal to the null-perpendicular space; and transmit a command tothe manipulator arm to drive the plurality of joints according to thecalculated movements so as to effect the desired end effector movementconcurrent with the desired movement of the one or more joints.
 14. Thesystem of claim 13 wherein the one or more joints defining a subspace ofthe joint space and the constraint is defined as one or more surfaceswithin the subspace.
 15. The system of claim 14, wherein the at leasttwo joints have independent joints states such that the subspacecomprises at least two dimensions.
 16. The system of claim 13, whereinthe processor is configured such that calculating a facilitatingmovement comprises: defining an attractive potential field within thejoint space such that an increase in potential corresponds to anincreased distance between a calculated position of the one or morejoints and the constraint; determining a potential between thecalculated position and the constraint; and calculating the facilitatingmovement of the plurality of joints using the determined potential. 17.The method of claim 1, wherein the positional constraint comprises oneor more paths having at least one dimension, wherein the one or morepaths are defined within a subspace of the joint space defined by atleast two joints of the plurality of joints.
 18. The system of claim 14,wherein the one or more paths comprise a network of paths that arepiecewise continuous.
 19. The system of claim 14, wherein the at leasttwo joints comprise a first and a second joint, the second jointcoupling a distal portion of the manipulator arm having an instrumentshaft to a proximal portion of the manipulator arm and the first jointbeing disposed between a proximal base of the manipulator arm and thesecond joint, wherein movement of the first joint controls a pitch ofthe distal instrument shaft of the manipulator arm and movement of thesecond joint pivots the instrument shaft laterally relative to a planealong which the proximal portion of the manipulator arm extends.
 20. Thesystem method of claim 14, wherein a distal portion of the manipulatorarm is coupled with an instrument holder to releasably support asurgical instrument having an elongate shaft extending distally to theend effector, wherein the instrument shaft pivots about a remote centerduring surgery, and wherein the at least two joints comprise a first andsecond joint of the plurality of joints, the first joint comprising arevolute joint, a state of the first joint corresponding to an outerpitch of the instrument holder, the second joint comprising a revolutejoint distal of the first joint, a state of the second jointcorresponding to a lateral displacement of the instrument holderrelative a plane along which a portion of the manipulator arm proximalthe second joint extends, such that the subspace defined by the firstand second joints corresponds to the pitch of the instrument shaftversus the lateral displacement of the instrument shaft.
 21. The systemof claim 14, further comprising: an input device for receiving areconfiguration command to drive at least one joint to effect a desiredreconfiguration of the manipulator arm, wherein the processor is furtherconfigured to: calculate a reconfiguration movement of one or morejoints in response to driving of the at least one joint so that thecalculated reconfiguration movement combined with driving of the atleast one joint extends within the null-space of the Jacobian; drive theplurality of joints according to the calculated reconfiguration movementconcurrent while driving the at least one joint to effect the desiredreconfiguration of the manipulator arm while maintaining a desired stateof the end effector; and modify the constraint in response to thecalculated reconfiguration movement.
 22. The system of claim 21, whereinthe processor is configured such that modifying the positioned-basedconstraint comprises translating a position or orientation of theconstraint within the subspace based on the calculated reconfigurationmovement.
 23. The system of claim 21, wherein the constraint comprises aplurality of alternatively selectable constraints, and wherein theprocessor is configured such that modifying the constraint comprisesselecting one of the plurality of constraints in response to thecalculated reconfiguration movement.
 24. The system of claim 16, whereinthe processor is further configured to calculate the facilitatingmovement by determining a movement of the plurality of joints within thejoint space using the determined potential and projecting the movementonto a null-space of the Jacobian to calculate joint velocities thatextend the joints along the constraint, thereby providing the increasedrange of movement of the one or more joints.
 25. The system of claim 21,wherein the processor is further configured with a tissue manipulationmode and a clutch mode, the processor in the tissue manipulation modecalculating the joint movements to provide the desired end effectormovement in response to the end effector manipulation command, and theprocessor in the clutch mode driving at least one joint in response toan external articulation of another joint while maintaining a givenstate of the end effector.
 26. The system of claim 25, furthercomprising: a clutch input for changing between the clutch mode and themanipulation mode, wherein modifying the constraint occurs in responseto reconfiguration of the one or more joints within the clutch mode. 27.The system of claim 13, wherein the processor is further configured to:calculate a collision avoidance movement to avoid a collision betweenthe manipulator arm and an adjacent manipulator arm, wherein thecollision avoidance movement is calculated within the null-space of theJacobian to avoid collisions while maintaining the desired state of theend effector; and overlay the collision avoidance movement with thefacilitating movement so as to avoid collisions while effecting thedesired movement of the one or more joints while increasing the range ofavailable joint movement.
 28. The robotic system of claim 25, whereineach joint of the manipulator assembly has an associated joint degree offreedom, and wherein the processor in the clutch mode is configured todrive the at least one joint in response to manual articulation of theother joint so as to provide the manipulator assembly with an effectiveclutch degree of freedom, the clutch degree of freedom differing fromeach of the joint degrees of freedom.
 29. The robotic system of claim28, wherein the at least one joint driven by the processor in the clutchmode comprises some or all of the joints of the manipulator assembly,the processor in the clutch mode configured to drive the manipulatorassembly in response to manual articulation of a plurality of the jointsof the manipulator assembly so that the manipulator assembly has aplurality of effective degrees of freedom when the processor is in theclutch mode.
 30. The system of claim 19, wherein at least some of thejoints comprise remote center joints mechanically constrained to pivotalmovement about a remote center along an insertion axis and adjacent aminimally invasive aperture through which the instrument shaft of thedistal end effector extends.
 31. The system of claim 30, wherein thefirst joint comprises one joint within a parallelogram linkage systemincluding: a parallelogram linkage base coupled to the base for rotationabout a first remote center axis intersecting the remote center; a firstlink having a first link proximal end and a first link distal end, thefirst link proximal end coupled to the parallelogram linkage base at abase joint, the first link distal end configured to support the tool; asecond link having a second link proximal end and a second link distalend, the second link proximal end coupled to the first link distal end,the second link distal end configured to support the tool so that aninsertion axis of the tool is constrained to rotation about a secondremote center axis intersecting the remote center, wherein movement ofthe links and joints of the parallelogram linkage system areinterrelated such that movement of the first joint in combination withthe other joints of the parallelogram linkage system determines thepitch of the instrument shaft relative to a remote center axisintersecting the first joint.